Do Now 1/17/12
 Take out HW from Friday.
 Practice worksheets 4.5 B & C
 Copy HW in your planner.
 Text p. 174, #1-12 all, 15, 16, 19, & 20
 Measurements of your bedroom (length & width) and at least 4 objects (bed, dresser, desk, etc…)
 Quiz sections 4.4 – 4.6 Friday
 Chapter 4 Test Tuesday 1/24
 Be ready to copy POTW #7




1) 60 cm
2) 44 °
3) 21 °
 4) 12 in
 5) 2.8 ft
 6) 16.5 ft



1) 21.6 yd
2) 56 °
3) 26 °
 4) 22.1 m
 5) 9.5 meters
 6) 28 feet
 7) 225 inches
 8) 112 feet

 SWBAT understand ratios and proportions in scale drawings and use ratios and proportions with scale

A proportional two-dimensional drawing of an object. Its dimensions are related to the dimensions of the actual object by a ratio called the SCALE FACTOR.

Identify the scale factor.
Caution!
A scale factor is always the ratio of the model’s dimensions to the actual object’s dimensions.
Length (in.)
Width (in.)
Room
144
108
Blueprint
18
13.5
blueprint length room length
=
18
144
Length (in.)
Wing span (in.)
Model Aircraft
12
18
Blueprint
2
3 blueprint length aircraft length
=
=
2
12
1
6

the SCALE of a drawing, map, or model relates the dimensions of the drawing, map, or model to the actual dimensions.
Write and solve a proportion to find the distance d between Cleveland and
Cincinnati if the distance on the map is about 4.2 centimeters.
1
85
=
4.2
d centimeters kilometers
1 d = 85 4.2
Cross products property d = 357
Simplify.

A proportional three-dimensional model of an object.

A dinosaur model kits sold at a hobby store has a scale of 1 ft : 25 ft.
A completed model of the dinosaur is 1.6
feet long. Estimate the actual length of the dinosaur.
SOLUTION
Write and solve a proportion to find the length g of the dinosaur .
1
25
=
1.6
g
1 ∙ g = 25 ∙ 1.6
g = 40
Cross products property
Simplify.
The actual length of the dinosaur is about 40 feet.

A model of a space shuttle has a scale of 1 : 52.
The space shuttle has a wingspan of 78 feet.
Find the model’s wingspan.
SOLUTION
Write and solve a proportion to find the wingspan w of the space shuttle .
1
52
= w
78
1 ∙ 78 = 52 ∙ w
1.5 = w
Cross products property
Simplify.
The wingspan of the model is 1.5 feet.

A scale drawing of a basketball court has a scale of 1 inch : 9 feet.
The basketball court is 94 ft by 50 ft. Find the dimensions of the court in the scale drawing.
1 in
9 ft
 L in
94 ft
1 in
9 ft
 W
50 in ft
1 ∙ 94 = 9 · L
L = 10 4/9in
1 ∙ 50 = 9 ∙ W
W = 5 5/9in

A scale drawing of a basketball court has a scale of 1 inch : 9 feet.
The free throw line is 15 feet from the backboard. How far is it in the scale drawing?
1 in
9 ft
 b in
15 ft
1 ∙ 15 = 9 · b b = 1 2/3in

 Text p. 174, #1-12 all, 15, 16, 19, & 20